The 59-year-old joined the IAAF council in 2003 but said he was only able to have a "limited focus" on the sport while he was chairman of the London 2012 organising committee.

"For 10 or 11 years, I was extremely busy in bidding or delivering a London Games," he said. "I didn't have the advantage of having a single focus on athletics."

Will Russia return for Rio 2016?

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Russia doping crisis in 60 seconds

Coe said Russia would only be readmitted to international competition "when we think they are in a position to deliver safe and secure systems to their athletes and not a moment before".

He added: "What we've said to them is, 'your clean athletes will only be appearing in international competitions again when we are entirely satisfied that you have done what we have asked you to do'. We haven't set artificial barriers. We haven't set easy, attainable targets.

"Wada has to make sure Russia's anti-doping is compliant as well."

Asked whether that would be before this summer's Rio Olympics, he said: "We're not saying that - let's see where we get to before we put an artificial time limit on it."

On Saturday, Russia named Dmitry Shlyakhtin as the new head of its athletics federation. He said: "Going to the Olympic Games is task number one."

'I will change athletics within four years'

Coe said his "biggest challenge" is restoring the public's trust in athletics, but added: "It may be the case that the trust has not returned way beyond my term."

He added: "For the sport to believe, fundamentally, that clean athletes are in a position to deliver their God-given talents on a clean platform will take longer. This is not an exact science.

"The challenge is in two key areas. One is to change the corporate governance, the way we do business within the sport, within the federation. The other is to return trust back to the track and that is primarily and overwhelmingly a simple principle - it is to get the cheats out of the sport as quickly as we can."

Coe said he would make the changes "well within four years".

'I have answered every question'

Coe was asked whether he would be willing to take a lie-detector test to prove he was telling the truth about his time working at the IAAF.

He said: "I have answered every question. With all due respect, I am answering questions virtually every hour of the day in virtually every forum."